Auto makers, parts suppliers and dealers are joining forces to push back against the Trump administration’s proposal to apply tariffs of up to 25% on vehicles and components imported into the U.S., contending the administration’s trade policy will backfire and lead to higher prices and lost jobs.

President Donald Trump has justified the proposed tariffs on national-security grounds and has argued that Germany and Japan don’t import enough U.S.-made vehicles. He has repeatedly called on both foreign and domestic auto makers...